This invention relates generally to satellite-based communication systems and, in particular, relates to methods and apparatus for delivering both low speed and high speed data services through a non-geosynchronous orbit (e.g., a low earth orbit) satellite communications system.
Conventional communications systems utilize terrestrial and satellite delivery systems to provide various messages, file transfers, video and other high speed media to and from user terminals. These messages may include the delivery of residential/commercial Internet access, distance learning, corporate training, and various broadcast applications. In addition, remote surveillance, remote database retrieval, satellite news gathering and disaster database recovery, and video conferencing. These systems are generally local in nature, or at most are national systems.
The introduction of Mobile Satellite Systems (MSS) allows both voice and low speed data delivery, however, these requirements of the above-mentioned higher speed data services have not yet been adequately addressed by conventional MSS. For example, low earth orbit (LEO) satellite systems such as Iridium(trademark) and Globalstar(trademark) are configured for voice and data up to 9.6 Kbps. While various means of concatenating multiple circuits of these voice circuits are available, such techniques can be difficult to introduce and manage.
It is a first object and advantage of this invention to provide an improved satellite-based communication system that overcomes the foregoing and other problems.
It is a further object and advantage of this invention to provide a method and system for delivering high speed data through a low earth orbit satellite system using a multi-terminal and a multi-gateway design.
The foregoing and other problems are overcome and the foregoing objects and advantages are realized by methods and apparatus in accordance with embodiments of this invention.
A mobile satellite system in accordance with these teachings delivers services between a user terminal and a gateway by employing a plurality of user terminals that cooperate with one another. These teachings, in addition to providing high speed radio frequency (RF) uplinks and downlink, enables a user to roam between regions using transportable and mobile terminals.
In accordance with these teachings there is provided a satellite-based communications system and a method for operating a satellite-based communications system. The system is of a type where communications between a user terminal and a gateway occur using an uplink band of frequencies between the user terminal to at least one satellite and in a downlink band of frequencies between the at least one satellite and the user terminal. The satellite-based communications system includes a first transceiver at the user terminal, referred to herein as a dual user terminal or dual terminal, for transmitting and receiving voice and data in the first and second bands of frequencies using a maximum data rate (e.g., a conventional MSS maximum data rate of 9600 Baud); and further includes a second transceiver at the user terminal for transmitting and receiving data in the first and second bands of frequencies using a second data rate that exceeds the maximum data rate. The uplink band of frequencies may include the L-band, and the downlink band of frequencies may include the S-band. A feederlink operates between the gateway and the at least one satellite, where the feederlink operates in a third band of frequencies, such as the C-band.
The gateway is a dual gateway that includes a first interface to voice and data signals and circuitry for transmitting and receiving the voice and data signals using the maximum data rate, and further includes a second interface to data signals and circuitry for transmitting and receiving the data signals using the data rate that exceeds the maximum data rate. The first and second interfaces and circuitry, and the first and second transceivers, may operate simultaneously.
In the preferred embodiment user terminal registration and control signals are transmitted and received using the first transceiver, for example, using the conventional MSS data rates and signaling protocols.
The user terminal may include at least one pointable antenna, and in this case information used for pointing the at least one antenna is received from the gateway using the first transceiver, for example, using the conventional MSS data rates and signaling protocols.
In a preferred, but not limiting, embodiment the first transceiver is a portion of a Mobile Satellite Service (MSS) terminal that is detachable from the user terminal for being operated as a stand-alone unit for transmitting and receiving voice and data signals in the first and second bands of frequencies using the maximum data rate. In this case it is preferred that the second, higher data rate transceiver remain fully operational. In another embodiment the first transceiver could include only a packet data modem, or a packet data modem could be used to replace the MSS terminal upon its detachment from the second terminal, thereby enabling call set-up and tear-down functions to continue. In a further embodiment two of the MSS terminals could be used, such that if one is removed the other, remaining one, can be used for setting up and tearing down calls.
In a preferred embodiment the gateway includes a PSTN or equivalent interface for voice and data signals and circuitry for transmitting and receiving the voice and data signals using the maximum data rate, and further includes an Internet interface for data signals and circuitry for transmitting and receiving the Internet data signals using the data rate that exceeds the maximum data rate.
In a further embodiment the gateway further includes transceivers for transmitting and receiving data with another gateway, via at least one satellite, in at least one of the first and second bands of frequencies.